1#!/usr/bin/env perl
2
3# Find functions making recursive calls to themselves.
4# (Multiple recursion where a() calls b() which calls a() not covered.)
5#
6# When the recursion depth might depend on data controlled by the attacker in
7# an unbounded way, those functions should use iteration instead.
8#
9# Typical usage: scripts/recursion.pl library/*.c
10#
11# Copyright The Mbed TLS Contributors
12# SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
13
14use warnings;
15use strict;
16
17use utf8;
18use open qw(:std utf8);
19
20# exclude functions that are ok:
21# - mpi_write_hlp: bounded by size of mbedtls_mpi, a compile-time constant
22# - x509_crt_verify_child: bounded by MBEDTLS_X509_MAX_INTERMEDIATE_CA
23my $known_ok = qr/mpi_write_hlp|x509_crt_verify_child/;
24
25my $cur_name;
26my $inside;
27my @funcs;
28
29die "Usage: $0 file.c [...]\n" unless @ARGV;
30
31while (<>)
32{
33    if( /^[^\/#{}\s]/ && ! /\[.*]/ ) {
34        chomp( $cur_name = $_ ) unless $inside;
35    } elsif( /^{/ && $cur_name ) {
36        $inside = 1;
37        $cur_name =~ s/.* ([^ ]*)\(.*/$1/;
38    } elsif( /^}/ && $inside ) {
39        undef $inside;
40        undef $cur_name;
41    } elsif( $inside && /\b\Q$cur_name\E\([^)]/ ) {
42        push @funcs, $cur_name unless /$known_ok/;
43    }
44}
45
46print "$_\n" for @funcs;
47exit @funcs;
48